Use of the Olson database (Re: Basic rationale of the KEP #2 design)

Bernhard Reiter bernhard at
Thu Mar 3 12:24:27 CET 2011

Hi Joon,

Am Donnerstag, 3. März 2011 11:31:38 schrieb Joon Radley:
> My understanding special use case that is driving KEP2 is as follows:

this answer and my last email send a minute ago time-crossed,
I did try explain the three use cases better in my other email
without having read this one.

> When an appointment is create by a special user the time for that user
> remains the same regardless of change in daylight savings time.

Okay, let try to rephrase to show I did understand:
You are saving one object E in a folder in timezone Berlin for User A
who is in Berlin.

> The rest of 
> the users appointments in the UI must now reflect a time adjusted so that
> the special users can still have his/her meeting at the same time. 

User B and C also access the same folder with E, but live in Toronto
and Tokio. So now E has to be displayed according to Toronto and Tokio
time. And  you directly load a serialized E into Outlooks memory.

> Two 
> problems with this:
> 1) The Outlook UI is immutable and can change at any time. So there is no
> way to enforce the change in Outlook without rewriting all the objects not
> in the same time zone as the special user, when the daylight savings
> settings changes for the user. 

Well it would be one appointment E and if it is new, of course
the timezone would need to be considered. If A changes E, of course the object
must be rewritten. As each object as the timezone label saved you can
do the writing when you get a new version of E.

With rewriting you mean that if the timezone database changes, you could need
to rewrite all objects of B and C, so their appointments are in the right 
place? As such changes rarely happen, this sounds feasable to me.

> 2) Since no one knows if Outlook is using 
> the Olsons database in the back ground there is no guarantee that they will
> display the zone as expected by other clients. This can be hacked to a
> large degree but full compatibility is not possible.

Would it be workable if we would limit the possibilities to a subset
of Olson then?

> So yes on the model side it is possible to try and translate between the
> Windows and Olsons zone, but the use case mention cannot be enforced in the
> Outlook UI without extreme measures.

I am not sure I have fully grasped this UI problem. I would not expect
the UI as in the event editor or the calender view being in need of a change.
(Except when we force to display the saved tiemzone, which is why I'd objected 
at that point.) I appreciate if you could get me maybe an example.


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